Method for locating the position of members relative to each other

ABSTRACT

Energy from a point source is directed through a plurality of non-visible structures having known dimensions in a given plane. Variations in the density of the material traversed by the energy vary the intensity of the energy reaching a photographic film. Within the plane including the energy source and the film, the distance from the source to each of the structures determines the lateral dimensions and the relative position of the structure&#39;&#39;s image on the film. Given the distance between the source and the film, the lateral dimensions of the structures and the lateral position, size and intensity of the image cast by each of the structures on the film, the relative location of all such structures with respect to the known position of a reference structure may be determined either graphically or mathematically. The device employed in the practice of the present invention includes a source of radio active energy carried in a camera housing which supports the source at a known, fixed distance from the reference structure. A film holder mounts the film behind the non-visible structures so that energy emitted from the source travels through the structures before striking the film. A small aperture in the camera housing focuses the energy causing it to radiate from a point. In use, the housing is flooded with water, lowered below the water surface and positioned about a subsurface well structure. The water in the housing is replaced with air after the housing is in place to reduce energy attenuation caused by the water.

United States Patent 91 Montgomery et al.

[ METHOD FOR LOCATING THE POSITION OF MEMBERS RELATIVE TO EACH OTHER[75] Inventors: James William Montgomery; Michael D. Reifel, both ofHouston,

Tex.

[73] Assignee: Tenneco Oil Company, Houston,

Tex.

[22] Filed: Aug. 20, 1971 [21] App1.No.: 173,535

Primary Examiner-James W. Lawrence Assistant Examiner-Harold A. DixonAttorney-Eugene S. Coddou and Carlos A. Torres [5 7] ABSTRACT Energyfrom a point source is directed through a plu- [451 May 22, 1973 ralityof non-visible structures having known dimensions in a given plane.Variations in the density of the material traversed by the energy varythe intensity of the energy reaching a photographic film. Within theplane including the energy source and the film, the distance from thesource to each of the structures determines the lateral dimensions andthe relative position of the structures image on the film. Given thedistance between the source and the film, the lateral dimensions of thestructures and the lateral position, size and intensity of the imagecast by each of the structures on the film, the relative location of allsuch structures with respect to the known position of a referencestructure may be determined either graphically or mathematically.

The device employed in the practice of the present invention includes asource of radio active energy carried in a camera housing which supportsthe source at a known, fixed distance from the reference stnicture. Afilm holder mounts the film behind the non-visible structures so thatenergy emitted from the source travels through the structures beforestriking the film. A small aperture in the camera housing focuses theenergy causing it to radiate from a point. In use, the housing isflooded with water, lowered below the water surface and positioned abouta subsurface well structure. The water in the housing is replaced withair after the housing is in place to reduce energy attenuation caused bythe water.

8 Claims, 3 Drawing Figures PATENTEU HAY 2 2 I975 c/AMES W MONTG OM53)/4 MICHAEL D. EE/FEL I N VEN TOR.

filwwliiau A TTORNEY METHOD FOR LOCATING THE POSITION OF MEMBERSRELATIVE TO EACH OTHER BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to means and methods fordetermining the position of non-visible structures relative to a pointhaving a known location. In a specific application, the presentinvention relates to means and methods for determining the position in ahorizontal plane of tubular metallic well conduits (such as tubingstrings and easing strings) with respect to a surrounding casingconductor string where the tubular conduits included within theconductor string extend vertically and have known diameters.

2. Description of the Prior Art The assignee of the present inventionhas developed a technique for bringing offshore well blowouts undercontrol by a method which includes opening access windows through thecasing string below the water surface and above the mud line. Theseaccess openings can be formed by cutting with a torch, mechanicalsawing, or with the use of shaped charges which, when detonated cut outthe casing wall in a configuration determined by the position and typeof charge employed. It

is desirable to know the exact position of casing and tubing stringscontained within the external casing so that the appropriate shapedcharge may be employed and the openings may be formed at the mostconvenient location. The method and apparatus employed in this techniqueare more fully described in US. Patent application Ser. No. 29,091,filed Apr. 16, 1970 now US. Pat. No. 3647000 entitled METHOD FOR CON-TROLLING WELL BLOWOUTS and assigned to the assignee of the presentinvention.

In the past, the position of tubular conduits contained within asurrounding conduit has been determined by the use of separate X-rayexposures made at right angles to each other. When applied to thepositioning of submerged well conduits as contemplated in the primaryapplication of the present invention, the equipment associated withX-ray techniques is cumbersome and difficult to handle. Moreover, therequirement for making two right angle exposures increases the timerequired to obtain the necessary information. Where the two right angleexposures are made simultaneously, appropriate shielding must beemployed to prevent interference thus further increasing the complexityof the technique and adding to the possibility that the informationobtained ,will be inaccurate.

The prior art has also employed sonic techniques in an attempt toestablish the relative location of structures contained within asurrounding casing or conductor string. Such techniques have generallyproven unreliable and provide only an approximation of structurallocations.

In the practice of the well control method described before, it isimperative that the relative location of the casing and tubing stringscontained within the conductor string be determined as quickly and asaccurately as possible. The equipment employed must be capable of beingpositioned under water by divers who often are dressed in relativelyheavy, cumbersome diving gear.

SUMMARY OF THE INVENTION In the method of the present invention, therelative location of one or more non-visible structures having knowndimensions within a given plane is determined with reference to a knownreference point in the plane by means of a quick and simple, singleexposure technique. In this technique, energy from a point source in theplane is radiated through the structures. Energy passing through thestructures strikes a sensitive medium such as photographic film andforms images of the intervening structures on the film s surface.

The intensities of the images vary as a function of the density of thematerials traversed by the energy. The dimensions of the imagesdetermine the distances of the structures from the source and thelocations of the images on the film are employed to establish thelateral positions of the structures. The locations may be obtainedthrough mathematical solution or through graphical scaling. In thepreferred form, the images of the film itself are used as markers andfull scale graphical scaling is employed to determine the positions ofthe unknown structures.

As compared with prior art techniques, the method of the presentinvention provides a straightforward procedure which afiords significanttime savings, and eliminates the danger associated with simultaneousright angle exposures to X-rays. The apparatus of the present inventionincludes a source of energy which preferably is radium or other radioactive substance. The source is located at one end of a camera housingand the other end of the housing is configured to conform to the tubularstructure to which it is attached. The radio active material within thehousing is confined within a suitable shielded structure until amanually controlled shutter is moved to open an aperture through whichenergy from the source may be focused. In the preferred form of theinvention, the aperture cooperates with the source to provide a pointsource. The source is fixed with respect to the structures to be locatedby engagement between the camera housing and the reference structure.Suitable waterproofing seals or packing may be provided along the areaof contact between the housing and the reference structure. Vent cocksare provided so that the internal housing area may be evacuated of waterand filled with air.

Two film strips with different exposure rates are positioned on theopposite side of the energy source in a film holder so that thestructures to be located are between the film strips and the source. Thefilm holder is held in position by suitable attachment with the camerahousing. Energy traversing the structures produces images on the filmwhich vary in light intensity dependent upon the density of thestructures traversed by the energy. The density variations producedifferences in images, colors ranging between a light gray to black withadjoining lines between images of different shades corresponding to theintersection with the film of projection lines extending from the pointsource, tangent to the external boundaries of the non-visiblestructures.

By analyzing the size, position and color of the images, and knowing theposition of the point source and the position of the film, structureshaving known dimensions within the plane of the measurement may bepositively located.

The foregoing and other features and advantages of the present inventionwill be more fully appreciated from the following specification,drawings and related claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1. is a partial verticalelevation, partially broken away illustrating the assembly of thepresent invention positioned about a well structure below the surface of5 DESCIRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1,the apparatus of the present invention is illustrated generally at inposition about a tubular conductor casing string 11 surrounding aninnercasing 12 which in turn surrounds two tubular production strings l3and 14. It will be appreciated that the position of the conductor casing11 is known and may function as a reference structure while thepositions of the structures 12, 13 and 14 are unknown and are to belocated with respect to the reference structure. The apparatus 10includes a camera housing 16 and a film holder 17 secured to each otherby springs 18.

Comparing FIGS. 1 and 2, it may be appreciated that the enclosure ofcamera housing 16 is substantially triangular in one dimension andincludes a curved end 16a adapted to engage and conform to the externalsurface of the conductor casing 11. A suitable packing or sealingmaterial 16b is disposed adjacent the intersection of the box end 160and the conductor casing 11 to provide a leakproof seal preventing waterfrom entering internal portions 160 of the camera housing.

The remote end of the camera housing is provided with a handle 16d whichis employed during the positioning of the housing 16 about the conductorpipe. A manually operable shutter control l6e is employed to regulateopening and closing of a small circular aperture (not shown) whichexposes a radio active material (not illustrated) contained within ashielded enclosure 16f formed at the remote end of the housing 16. Theaperture and energy source align substantially along the dotted line Cso that with the shutter opened, energy emitted from the apertureopening into the energy source radiates outwardly from the source in theform of rays' diverging from a point source. This is representedschematically in FIG. 3 wherein the rays are depicted generally at R andthe point source location is indicated schematically at S.

Before lowering the apparatus 10 into the water, the area 160 is filledwith water so that the device will tend to sink through the water. Oncethe desired subsurface location has been reached, the box portion 16 ispositioned as indicated in FIG. 1 and the springs 18 are snapped ontothe film holder 17. The springs 18 maintain the film holder and film ata fixed location relative to the conductor casing 11 and relative to thepoint source S.

Two elongate strips of film 20 and 21 are positioned in the film holder17. The strips are preferably protected by being encased in a waterproofbag or covering. Preferably, the film strips 20 and 21 have differentexposure rates so that increased information may be obtained from afixed exposure time. As will be seen,

the film functions as a measuring means to indicate the intensity ofenergy passing through the structures.

With the apparatus in the position illustrated in FIGS. 1 and 2, a ventcock 22 is opened and air is applied to a second vent cock 23 to replacewater contained within the area 160 with air. The water is replaced withair since it does not attenuate the energy radiated from the pointsource S to the same extent as water. Suitable weights (not illustrated)or other means may be employed to prevent the camera housing 16 fromrising in the water due to the increased buoyancy caused by filling thearea 160 with air. When the area 160 has been evacuated of water, thecocks 22 and 23 are closed and the shutter control l6e is opened topermit energy from the source S to radiate through the camera housingand through the structures 11, 12, 13 and 14 causing images of thestructures to be formed on the film strips 20 and 21.

The various images appearing on the film 20 and 21 are depictedschematically in FIG. 3 as 20a through 20g. The color of the imagesvaries as a function of the density of the matter traversed by theenergy. Image 20d is the lightest in color since the density of thematter between it and the source was greater than that between thesource and the other images. The locations of density change linesmarking the separation between images 20a through 20g are employed tolocate the relative lateral positions of members 12, 13 and 14 withrespect to the surrounding conductor casing 11. Thus, as can be seen byreference to FIG. 3, lines projected from the point source S tangent tothe external surfaces of the structures 11, 12, 13 and 14 strike thefilm strip images at the density change lines between adjacent images.

Given the distance X and the external dimensions of structures 11, 12,13 and 14, the relative location of each of these structures can bedetermined from the positioning and size of the images 200 through 20f.Such a solution may be effected either through graphical scaling orthrough mathematical solution.

Where full scale graphical solutions are employed, the film 20 (or 21)may be positioned at a fixed distance from a point representing thepoint source S with lines representing the energy rays R drawn from thepoint source to the density change lines between images. By this means,a full scale radiating grid is formed and full sized templates of thestructures 11, 12, 13 and 14 may then be moved between the grid lineswhich strike the exposed film at the density change lines until thetemplates are tangent to the grid lines. The resulting position of thetemplates provides a precise indication of the location of each of thecorresponding structures.

In testing, using a 100 curie iridium 192 element for the source and two21" strips of Ansco A and DuPont NDT- film for the sensitive mediums,suitable images were obtained on the film in approximately 15 to 30minutes.

With the apparatus and method of the present invention, it is evidentthat the positions of tubing and casing strings within a supportingstructure can be accurately determined preliminary to the application ofshaped charges or other cutting means to remove portions of thesurrounding structure. The technique permits the formation of windowsthrough the casing at the point where the tubing strings are mostconveniently located and also permits placement of charges and cuttingmechanisms at a position which will minimize danger to the interlyingstructures.

While the apparatus has been described as employing a linear film holderwith a source spaced from the conductor casing, it will be appreciatedthat the film holder and film may be curved or may be wrapped about thetubular conductor string or the source may be directly adjacent theconductor string.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof, and various changes in the size,shape and materials as well as in the details of the illustratedconstruction may be made within the scope of the appended claims withoutdeparting from the spirit of the invention.

We claim:

1. A method of locating the position within a given plane of one or morefirst structures having known dimensions along a given direction in saidplane comprising the steps of:

a. radiating energy from a source of radiant energy positioned at afirst location in said plane where said first location is known withrespect to a known reference point in said plane;

b. positioning measuring means along a second location in said planewhere said second location is known with respect to said referencepoint, said measuring means being located to intercept the energypassing through said first structures and including means for providingimages of said first structures which images vary in intensity dependingupon the density of matter traversed by said energy, and vary indimension within said plane depending upon the dimensions within saidplane of said first structures and the distances in said plane of saidfirst structures from said source and vary in location in said planedepending upon the locations of said first structures in said plane; andsolving for the planar position of said first structures with respect tosaid reference point using the planar dimensions and positions of saidimages, the planar distance between said source and said measuringmeans, and the planar dimensions of said first structures.

2. A method as defined in claim 1 including the step of solving for theplanar positions of said first structures by graphical scaling in whichsaid images, said energy source and said reference point are depicted ina graphical representation and representations of said first structuresare positioned on said graphical representation at the locationsrequired to correspond to said images.

3. A method as defined in claim 1 including the steps of:

a. employing photographic film for said measuring means; and

b. employing radium as said energy source whereby radiated energy fromsaid radium source passing through said first structures forms lightvariant images on said photographic film.

4. A method of locating the lateral position of one or more tubularmembers extending axially within a surrounding body where the lateraldimensions of said tubular members and said surrounding body are knowncomprising the steps of:

a. radiating energy from a source point through said tubular members andsaid surrounding body along a lateral plane which is substantiallyperpendicular to the axial direction of said tubular members;

b. exposing a sensitive measuring means to the energy within said planetransmitted through said surrounding body and said tubular members forforming images on said measuring means which images vary in intensitydepending upon the density of the matter traversed between said sourcepoint and said measuring means; and

solving for the lateral positions of said tubular members within saidsurrounding body using the lateral dimension of said tubular members,the distance between said source point and said measuring means and thedimensions and position within said lateral plane of the images cast bysaid tubular members.

5. A method as defined in claim 4 wherein:

a. said source point energy is derived from a radio active material; and

b. said measuring means includes photographic film.

6. A method as defined in claim 4 wherein the locations of said tubularmembers are determined by graphical scaling.

7. A method as defined in claim 5 wherein the locations of said tubularmembers are determined by graphical scaling.

8. A method as defined in claim 5 wherein the locations of said tubularmembers is obtained by mathematical solution.

1. A method of locating the position within a given plane of one or morefirst structures having known dimensions along a given direction in saidplane comprising the steps of: a. radiating energy from a source ofradiant energy positioned at a first location in said plane where saidfirst location is known with respect to a known reference point in saidplane; b. positioning measuring means along a second location in saidplane where said second location is known with respect to said referencepoint, said measuring means being located to intercept the energypassing through said first structures and including means for providingimages of said first structures which images vary in intensity dependingupon the density of matter traversed by said energy, and vary indimension within said plane depending upon the dimensions within saidplane of said first structures and the distances in said plane of saidfirst structures from said source and vary in location in said planedepending upon the locations of said first structures in said plane; andc. solving for the planar position of said first structures with respectto said reference point using the planar dimensions and positions ofsaid images, the planar distance between said source and said measuringmeans, and the planar dimensions of said first structures.
 2. A methodas defined in claim 1 including the step of solving for the planarpositions of said first structures by graphical scaling in which saidimages, said energy source and said reference point are depicted in agraphical representation and representations of said first structuresare positioned on said graphical representation at the locationsrequired to correspond to said images.
 3. A method as defined in claim 1including the steps of: a. employing photographic film for saidmeasuring means; and b. employing radium as said energy source wherebyradiated energy from said radium source passing through said firststructures forms light variant images on said photographic film.
 4. Amethod of locating the lateral position of one or more tubular membersextending axially within a surrounding body where the lateral dimensionsof said tubular members and said surrounding body are known comprisingthe steps of: a. radiating energy from a source point through saidtubular members and said surrounding body along a lateral plane which issubstantially perpendicular to the axial direction of said tubularmembers; b. exposing a sensitive measuring means to the energy withinsaid plane transmitted through said surrounding body and said tubularmembers for forming images on said measuring means which images vary inintensity depending upon the density of the matter traversed betweensaid source point and said measuring means; and c. solving for thelateral positions of said tubular members within said surrounding bodyusing the lateral dimension of said tubular members, the distancebetween said source point and said measuring means and the dimensionsand position within said lateral plane of the images cast by saidtubular members.
 5. A method as defined in claim 4 wherein: a. saidsource point energy is derived from a radio active material; and b. saidmeasuring means includes photographic film.
 6. A method as defined inclaim 4 wherein the locations of said tubular members are determined bygraphical scaling.
 7. A method as defined in claim 5 wherein thelocations of said tubular members are determined by graphical scaling.8. A method as defined in claim 5 wherein the locations of said tubularmembers is obtained by mathematical solution.